1. Field of the Invention
The present invention relates generally to the fields of molecular virology and protein chemistry. More specifically, the present invention relates to the use of Human and Simian Immunodeficiency Virus (HIV/SIV) Vpx and Vpr proteins, or amino acid residues that mediate their packaging, as vehicles for delivery of proteins/peptides to virions or virus-like particles and uses thereof.
2. Description of the Related Art
Unlike simple retroviruses, human and simian immunodeficiency viruses (HIV/SIV) encode proteins in addition to Gag, Pol, and Env that are packaged into virus particles. These include the Vpr protein, present in all primate lentiviral, and the Vpx protein, which is unique to the HIV-2/SIVSM/SIVMAC group of viruses. Since Vpr and Vpx are present in infectious virions, they have long been thought to play important roles early in the virus life cycle. Indeed, recent studies of HIV-1 have shown that Vpr has nucleophilic properties and that it facilitates, together with the matrix protein, nuclear transport of the viral preintegration complex in nondividing cells, such as the macrophage. Similarly, Vpx-deficient HIV-2 has been shown to exhibit delayed replication kinetics and to require 2-3 orders of magnitude more virus to produce and maintain a productive infection in peripheral blood mononuclear cells. Thus, both accessory proteins appear to be important for efficient. replication and spread of HIV/SIV in primary target cells.
Incorporation of foreign proteins into retrovirus particles has previously been reported by fusion with gag. Using the yeast retrotransposon Ty1 as a retrovirus assembly model, Natsoulis and Boeke tested this approach as a novel means to interfere with viral replication. More recently, the expression of a murine retrovirus capsid-staphylococcal nuclease fusion protein was found to inhibit murine leukemia virus replication in tissue culture cells.
The prior art lacks effective means of delivering or targeting foreign, e.g., toxic proteins to virions. The present invention fulfills this longstanding need and desire in the art.
Vpr and Vpx packaging is mediated by the Gag precursor and thus must play an important role in HIV assembly processes. The present invention shows that Vpr and Vpx can be used as vehicles to target foreign proteins to HIV/SIV virions. Vpr1 and Vpx2 gene fusions were constructed with bacterial staphylococcal nuclease (SN) and chloramphenicol acetyl transferase (CAT) genes. Unlike Gag or Pol proteins, Vpr and Vpx are dispensable for viral replication in immortalized T-cell lines. Thus, structural alteration of these accessory proteins may be more readily tolerated than similar changes in Gag or Gag/Pol. Fusion proteins containing a Vpx or Vpr moiety should be packaged into HIV particles by expression in trans, since their incorporation should be mediated by the same interactions with Gag that facilitates wild-type Vpr and Vpx protein packaging.
Vpr and Vpx fusion proteins were constructed and their abilities to package into HIV particles were demonstrated. Fusion partners selected for demonstration were: staphylococcal nuclease because of its potential to degrade viral nucleic acid upon packaging and the chloramphenicol acetyl transferase because of its utility as a functional marker. To control for cytotoxicity, an enzymatically inactive nuclease mutant (SN*), derived from SN by site-directed mutagenesis was also used. This SN* mutant differs from wild-type SN by two amino acid substitutions; Glu was changed to Ser (position 43) and Arg was changed to Gly (position 87). SN* folds normally, but has a specific activity that is 106-fold lower than wild-type SN. Using transient expression systems and in trans complementation approaches, fusion protein stability, function and packaging requirements was shown. The present invention shows that Vpr1 and Vpx2 fusion proteins were expressed in mammalian cells and were incorporated into HIV particles even in the presence of wild-type Vpr and/or Vpx proteins. More importantly, however, the present invention shows that virion incorporated Vpr and Vpx fusions remain enzymatically active. Thus, targeting heterologous Vpr and Vpx fusion proteins, including deleterious enzymes, to virions represents a new avenue toward anti-HIV drug discovery.
In one embodiment of the present invention, there is provided a composition of matter, comprising: DNA encoding a viral Vpx protein fused to DNA encoding a virus inhibitory protein.
In another embodiment of the present invention, there is provided a composition of matter, comprising: DNA encoding a viral Vpr protein fused to DNA encoding a virus inhibitory protein.
In yet another embodiment of the present invention, there is provided a method of delivering a virus inhibitory molecule to a target in an animal, comprising the step of administering to said animal an effective amount of the composition of the present invention.
In still yet another embodiment of the present invention, there is provided a pharmaceutical composition, comprising a composition of the present invention and a pharmaceutically acceptable carrier.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention given for the purpose of disclosure.